The present invention relates in general to clutch release bearings, that is, devices adapted to operate the release mechanism of clutches, especially those for motor vehicles.
As is known, such clutch release bearings generally comprise an operating member which is controlled by an actuating member which is usually an actuating fork, a drive or thrust member which is urged by the operating member against the release mechanism of the clutch and coupling means for securing the drive or thrust member axially to the operating member.
In practice the operating member usually comprises a transverse flange on one side of which is mounted the actuating member and on the other side of which bears the drive or thrust member.
The present invention more particularly relates to such clutch release bearings in which the operating member is made of synthetic plastic material. To protect such a plastic operating member from the action of the actuating member which may, on account the contact pressure developed during each clutch disengagement operation, cause rapid deterioration, detrimental to long service life of the release bearing, it is common to provide a special metal bearing member against which the actuating member bears axially. Usually this metal bearing member comprises a plate which overlies the flange of the operating member on the side thereof remote from the drive or thrust member.
It has, however, been proposed to dispose the bearing member between the drive or thrust member and the transverse flange of the operating member. Such is the case, for example, in U.S. Pat. No. 3,390,927, French printed patent application No. 2,391,392 and at least some of the embodiments of U.S. patent application Ser. No. 184,629, filed Sept. 8, 1980, now U.S. Pat. No. 4,371,068 granted Feb. 1, 1983, assigned to the assignee of the present application.
In the U.S. Pat. No. 3,390,927 the bearing member to which the actuating member has access through the transverse flange of the operating member, has for this purpose local passageways of L-shaped profile necessitated by the fact that the since the clutch release bearing is not a self-centering release bearing its drive or thrust member is fitted against radial displacement on a cylindrical bearing surface of the bearing member which must be formed on an axial part of the bearing member.
Other than the fact that such an arrangement is not suited to self-centering operation in which limited radial shifting of the drive or thrust member is provided relative to the operating member in all directions in a plane perpendicular to the axis of the release bearing, it involves the use of a bearing member which is of relatively complex configuration and therefore is all the more expensive as thermal treatment is required to reinforce it against impacts, such thermal treatment not being possible before the part is in its ultimate configuration.
In French printed patent application No. 2,391,292 the bearing member is formed in one piece with one of the components of the drive or thrust member and it therefore has a relatively complex overall configuration thereby increasing production costs.
In above identified patent application Ser. No. 184,629, the bearing member comprises a part separate from the drive or thrust member but for reasons of its particular application, the bearing member has, as above, a relatively overall complex configuration and therefore is relatively expensive to manufacture.